Traditional LP engines have a vacuum lockoff device in their LP fuel system line. The vacuum lockoff device allows LP flow to the engine when a vacuum at the intake manifold is sensed by the vacuum lockoff device. When the vacuum lockoff device does not sense any vacuum in the intake manifold, LP flow in the fuel line to the carburetor is prohibited. A vacuum condition at the intake manifold is created when the engine is running or being cranked such as during starting. As long as the engine is running LP flow to the engine is allowed. When the engine stops, LP flow to the engine is prohibited. Accordingly, the vacuum lockoff functions as a safety device to make sure that LP flow to the engine is prohibited when the engine is shut off.
Such vacuum lockoff devices can make starting an LP engine difficult. As the engine is being cranked, the vacuum condition at the intake manifold is rather tenuous and fluctuates between a vacuum condition and a non-vacuum condition. Moreover, between recoil start pulls, a vacuum condition does not exist and LP fuel flow is prohibited.
The present invention solves this problem and results in an LP engine which can be much more easily started.